This invention relates generally to non-destructive testing apparatus and more particularly to apparatus for providing ultrasonic visualization of discontinuities in optically opaque materials.
As to the prior art, the usual means employed for ultrasonic imaging for determining concealed defects in materials utilizes a tank filled with water or oil in which both the specimen and ultrasonic transmitter are immersed. This necessitates the use of cumbersome test apparatus and the fact that the test specimen and ultrasonic transmitter are immersed in a liquid bath results in accompanying undesirable corrosion effects. This problem was recognized and overcome by apparatus disclosed in U.S. Pat. No. 3,572,088 entitled "Device for Conversion of Ultrasonic Images Into Visible Displays", O. R. Gericke, (the present co-inventor), et al. dated Mar. 23, 1971. There the test specimen is not immersed in a liquid medium. The apparatus disclosed, furthermore, produced monochromatic ultrasonographs which were displayed on a black and white closed circuit television monitor which was subsequently recorded, for example on a video tape recorder.